In adding or replacing suspended cables, such as electric, telephone, steel or other cables, a non-conductive cord is usually positioned over the top of a first pole or other point of suspension, moved along the ground to a second point of suspension, and positioned over the second point of suspension. The non-conductive cord is then attached to the end of the cable to draw the cable between the fixed points of suspension. When fixed to the elevated points of suspension, the cable forms a catenary curve.
Problems have been encountered when the wire must be suspended over natural or man-made obstacles such as highways, rivers and valleys.
To suspend a cable across a highway, heretofore, traffic has been interrupted as the non-conductive cord was drawn from the first point of suspension on one side of the highway to the second point of suspension on the other side of the highway. This created a hazardous condition for both the vehicles on the highway and the workmen who move the non-conductive cable across the highway. In addition, natural obstacles often pose an even greater problem; for example, a boat must be used to traverse a river.
It should be noted that the above procedure has been employed even if at least one cable is already in position between the points of suspension.
Heretofore devices have been devised to move along electrical conductors to string a second conductor parallel to the first conductor. Such devices are disclosed in U.S. Pat. Nos. 628,994; 695,504; 798,602; and 1,569,521.
Devices of the type described in the aforementioned patents have not enjoyed commercial success for stringing new cable or for re-wiring to replace damaged cable.
The devices heretofore devised were not adapted to move along strands of wire of different diameters and particularly were not adapted to pass obstacles, such as splices which are often encountered. Further, the devices were not equipped with a power source suitable for propelling the device along a long span of wire. The particular sources of power, such as spring powered drive wheels, immediately expend all of the power in the spring if the drive wheel becomes momentarily moved out of engagement with the cable along which the device is travelling.
Telephone cables often comprise a bundle of conductors about which a strand of wire is spirally wrapped such that the surface of the cable has an irregular surface. Splices in electrical conductors generally comprise a tubular sleeve which is cramped onto ends of conductors to connect the conductors together. A splice for copper wire might comprise a sleeve which is 3/8 of an inch in diameter and 4 inches long while a splice for larger aluminum conductors may comprise a sleeve which is 2 inches in diameter and 36 inches long.
The prior devices referred to above were not capable of moving along strands of wire of different diameters and particularly along a strand of wire which changes diameters intermediate points of suspension of the wire.